The long-term goal of the study are to reduce the sexual transmission of HIV and to reduce the prevalence of sexually transmitted infections (STI). The specific aims are 1) to measure the effect of nonoxynol-9 (N- 9) film use on the rate of HIV infection by comparing the rate of infection of women using condoms and N-9 film with that of women using condoms and placebo film, 2) to measure the effect of N-9 film on the rate of genital ulcers and symptoms of irritation by comparing the rate of genital ulcers and irritation of women using N-9 with that of women using placebo, and 3) to measure the effects of N-9 film use on the vaginal ecology by comparing the vaginal flora patterns before initiation of N-9 use with the flora patterns after N-9 use. A randomized, double-bind, multicenter, placebo-controlled trial conducted in Yaonde and Douala, Cameroon will be conducted. an N-9 film containing about 70 mg of N-9 will be compared with a placebo film with identical non-active ingredients, packaging, and labeling as the N-9 film. This product was chosen because it has been used in previous studies with women who had approximately the same frequency of sexual contact as the women of the proposed study, and was not associated with an increase in yeast infections or genital ulcers. About 1,000 women at high-risk for HIV infection will be randomized to receive either condoms and N-9 or condoms and placebo. The recruitment period will be for 1 year and the follow-up period will be for 1 year. Survival analysis techniques will be used for intent-to-treat analysis of the N-9 data. Data on demographic characteristics, potential confounders and effect modifiers will be collected at enrollment and during the follow-up period. Colposcopy will be used to assess genital epithelial disruption. Interim analyses will be reviewed by an oversight committee at 4 month intervals. This study will provide valuable information to women for those attempting to slow the rate of HIV infection among women.